Method for forming polyurethane cover on golf ball core

ABSTRACT

A method of making a golf ball having a core and outer polyurethane cover by placing a first portion of polyurethane in a first cavity and allowing the first portion of polyurethane to partially cure to a selected state of gel. The core is positioned within the cavity while the core is vertically and laterally centered within the cavity. A second portion of polyurethane is placed in a second cavity at a time subsequent to placing the first portion of polyurethane in the first cavity. The second portion of polyurethane is allowed to partially care. The first and second cavities are mated together to cure the polyurethane around the core.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/992,835filed Dec. 17, 1997, now U.S. Pat. No. 9,888,437, which is acontinuation of application Ser. No. 08/432,657 filed May 2, 1995, nowU.S. Pat. No. 5,733,428, which is a continuation of application Ser. No.08/185,667 filed Jan. 21, 1994 now abandoned, which is acontinuation-in-part of application Ser. No. 07/909,543 filed Jul. 6,1992, now abandoned.

BACKGROUND OF THE INVENTION

The use of urethane polymers has been proposed for golf ball covercompositions. One patent teaches initially forming two urethane shellblanks from which cover halves are made (U.S. Pat. No. 3,989,568).Another patent suggests forming a smooth cover and thereafter impressingdimples in the smooth cover (U.S. Pat. No. 5,006,297). Still anotherpatent describes a sequence of filling first half of a mold withurethane, inserting a ball center therein and later adding more urethaneto a second half and uniting the second with the first half (U.S. Pat.No. 3,147,324).

SUMMARY OF THE INVENTION

Broadly, the present invention is a method and apparatus for making agolf ball comprising treating a core as described herein, placing apolyurethane cover of selected composition thereon in which the treatedcore is positioned in a mold using a controlled alignment device forcentering the core during cover formation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is plan view of the core treating apparatus;

FIG. 2 is an elevational view of such apparatus;

FIG. 3 is an elevational view of alignable device for placing a treatedcore in a mold half;

FIG. 3a is a partial side elevational view of the alignable device;

FIG. 4 is a sectional view along line 4--4 of FIG. 3;

FIG. 5 is a plan view showing a mold being positioned in the alignmentdevice;

FIG. 6 shows apparatus for mixing polyurethane, dispensing it in a moldhalf and shows one mold half being inverted before mating with a secondmold half.

FIG. 7 shows a plan view of set-up mold;

FIG. 7a shows a side view of set-up core with alignment holes;

FIG. 8 is a graph plotting voltage vs. cps;

FIG. 9 is a graph plotting voltage vs. time;

FIGS. 10a and 10b are tables of process steps in a timed sequence;

FIG. 11 is a graph plotting hardness vs. spin rate;

FIG. 12 is a graph plotting initial velocity vs. wound ball size;

FIG. 13 is a front elevational view of an alternative embodiment of thecore alignment device;

FIG. 13a is a side elevational view of the alignment device;

FIG. 14 is a sectional view along line 14--14 of FIG. 3; and

FIG. 15 is a plan view of a mold half with a horizontal aligning railunit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning to the Figures, and in particular to FIGS. 1 and 2, dippingapparatus 10 includes a dip tank 12 filled to level 12a and agitated byelectric mixer 12m. Apparatus 10 also includes oval conveying rack 13with ball core carriers 16. Dip tank 12 is filled with latex bath 12b tolevel 12a and, if latex has been in tank 12 for a substantial length oftime, initial mixing of bath 12b in tank 12 should be carried out untiluniformity of bath 12b is reached. After such mixing golf ball cores 14are loaded at loading station 15 into holding carriers 16 eachcomprising a stem 16a and a holder ring 16b. During normal operationtank 12 is agitated by electric mixer 12m. Loaded carriers 16 arecarried by conveying rack 13 along and down to dip cores 14 for 1 to 60seconds into latex bath 12b. Rack 13 moves through a descending portion20, dipping portion 22 and ascending portion 24 of the carrier circuitto accomplish the latex dip core treatment. In wound cores the latexencapsulates the core with penetrate to a depth of about 0.050 inch andin solid cores the latex forms an encapsulating coating on the core of0.001-0.010 inch thick.

After the ball cores 14 exit dip tank 12, they pass into a curingchamber 25 in which heat, ultraviolet rays, or other means foraccelerating cure may be applied. It will be understood that some latexbath materials cure sufficiently under ambient conditions that curingchamber 25 is not required. Cores are unloaded at unload station 21.

In accordance with this invention, wound cores 14 preferably are latexdipped while dipping of solid cores 14 is optional. Depending on thenature of the latex material applied, the golf ball dip-treated cores 14can then be stored for a period of time for additional cure, or, if thelatex material is sufficiently cured at this point, the wound cores withthe latex dip encapsulate can be transported directly to the moldingarea for molding of the cover material.

Since the latex material generates low levels of ammonia fumes in thedip tank 12, it is preferred to have a vacuum hood 23 positioned abovethe dip tank 12. The vacuum hood 23 is preferably provided with means(not shown) for generating a clean air curtain about the periphery ofthe dip tank 12 to prevent escape of undesirable gasses. The curingchamber 25 can also be provided with suitable gas removal means.

As described above, the initial step of the process of the presentinvention is the dipping of the core in a latex bath. The preferred coreis a wound core but any core, molded or wound, may be treated by thepresent process. With a molded core the advantage of such latex diptreatment is the increased velocity attainable to golf balls made withsuch cores. With a wound core the advantages are increased velocity,reduction of flow of air into the cover material during cover formationand prevention of rubber strand unravelling.

It is important that a thermosetting, not a thermoplastic, latex beemployed so that the arrangement of the cover material to the coreencapsulated will not soften the encapsulating envelope and permit airto pass through it into the interstices in the windings of the woundcore or allow the rubber strands to unravel.

The thermosetting latex materials which are useful in the presentinvention are any materials which will withstand the temperatures atwhich the cover material is to be applied. This temperature will, ofcourse, depend upon the particular fluidization temperature of theselected cover material. Typical thermosetting latex materials which canbe used are: low ammonia, natural latex or pre-vulcanized natural latexwith or without penetrant. When using a polyurethane cover material, ithas been found that pre-vulcanized natural latex is particularlysuitable.

The preferred latex material, Heveatex brand Model H1704 pre-vulcanizednatural latex, is a partially pre-vulcanized material which has a60%-30% water dilution solids content. The preferred penetrant materialis Niaproof #4 (tetra decyl sulfate) sold by Niacet Corp. It isunderstood that non-latex encapsulating materials may also be used.

After latex coating, the cover is formed around the coated core bymixing and introducing the material in mold halves. Once mixed, anexothermic reaction commences and continues. It is important that theviscosity be measured over time, so that the subsequent steps of fillingeach mold half, introducing the core into one half and closing the moldcan be properly timed for accomplishing centering of the core coverhalves fusion and achieving overall uniformity.

The increase in the viscosity of the urethane mix over time is measuredby Vibrating Needle Curemeter (VNC) manufactured by Rapra TechnologyLimited. It is achieved by suspending a steel needle in the curingformulation. The needle is vibrated vertically by a small electrodynamicvibrator driven by a signal generator. Resistance to its movement isultimately recorded as the voltage output. Suitable viscosity range ofthe curing urethane mix for introducing cores 14 into the mold halves51, 59 is determined to be approximately between 2,000 cps-30,000 cps orbetween 60 mv-98 mv voltage output with the preferred range of 8,000 to15,000 cps (see FIG. 8). The time (gel time) at which the desiredviscosity range occurs for mold mating is measured from firstintroduction of mix into the top half mold 51a.

The dip coating of latex penetrates the interstices, crevices andopenings between the wound core threads to a depth of a fraction of aninch preferable about 0.050 inches and, as solidified, prevents asubstantial quantity of air from flowing from the interior of the coreinto the cover during its formation. A negligible amount of the latexremains on the outside of the wound core. With solid cores about0.001-0.010 inch is coated on the surface thus reducing the coverthickness by that amount. Small amounts of air passing through or aroundthe latex coating are not large enough to create noticeableimperfections in the cover as determined by visual inspection.

Turning to FIG. 3 and 3a, another step of the process is the formationof the cover on the wound core 12. To accomplish this step a centeringfixture is used. Fixture unit 30 includes box frame 32, stationarycentral guide mount 34 comprising fixed cylinder 35 and stationary guideblock 37. Guide block 37 has two (2) parallel passageways 37a, 37btherethrough for receiving movable rods 41, 42 in sliding verticalmovement. Rods 41, 42 are fixed to slide ball cup frame unit 44, throughback piece 40, which unit 44 carries ball cup 46 mounted on cup plate44b as described (see FIG. 3a). Ball cup 46 holds ball core 14 throughreduced pressure (or partial vacuum) in hose 46a. Ball cup frame unit 44includes base plate 44b, central opening 44a and upstanding back plate44c. Back support 40 is secured to back plate 44c. Ball cup 46 isadjustably secured to cup plate 44b through adjustable fasteners 49a, bwhich ride in slots 44s and 44t (FIG. 4). Cup 46 can be adjustedvis-a-vis plate 44b front and back along arrow A (FIG. 4).

To initially align ball core cup 46 in the proper position for moldingof cover material, a machined metal set-up mold 50 is used. Set-up mold50 is positioned by lowering unit 44 to permit pins 72, 73 to passthrough alignment holes 71a, 71b in mold 50. Rails 53 and 56 serve onlyto assist in placing the mold 50 under unit 44 and after mold 50 isproperly aligned it is spaced a few thousandths of an inch from eachrail 53, 56 (FIG. 7). With ball cup 46 free through loosened fasteners49a, b, alignment of cup 46 is accomplished by lowering ball cup 46until it sits on and contacts set-up core 70. Fasteners 49a, b aretightened when flush contact with ball cup 46 and set-up core 70 hasbeen made. Next, mechanical stop 39b is tightened in this position.Frame unit 44 is then raised from set-up mold 50 and set-up mold 50 isremoved from fixture 30.

More than one fixture unit 30 is used in the practice of this invention.With fixture unit 30 so aligned, the set-up mold 50 is removed and isready to be replaced with a ball core 14 and a series of regular moldhalves 51b, 51c, etc.

The core is centered by fixture unit 30 in the top mold half, as theninverted, to a tolerance of about 0.010 of an inch. Such tolerance isdescribed by determining the theoretical center of the core in the moldhalf and tolerating the actual core center, as fixtured, to be locatedup to 0.005 of an inch in any direction for the theoretical center.Since the actual center is tolerated to move 0.005 inch in any directionfrom the theoretical center, it can move over a range of 0.010 of aninch.

Turning to FIGS. 13-15, prime numbered elements correspond to elementson FIGS. 3-5. This alternative embodiment aligns each mold half 51, 59with respect to the fixture frame base 30b of frame 30' using ahorizontal rail alignment unit 66 which includes stationary mount block66m, positioned on fixture base 30b, a raised horizontal cross piece 66cwhich carries two (2) parallel alignment rails 66a, 66b having squarecross sections which rails 66a, 66b lie in mold end-to-end indentations67, 68. Each mold indentation 67 and 68 includes a horizontal wall 67a,68a and a vertical wall 67b, 68b. Rails 66a, 66b have tapered tips 66d,66e to assist in guiding and positioning mold halves 51', as each isslid in direction D to the position of FIG. 15. As a mold half 51' ismoved back against block 66m it is aligned and the mold half 51' isthereafter accurately positioned as pins 72' and 73' engage and move, asnecessary, the mold half 51' during fixture descent. The spacingsbetween block 66m and rails 66a, 66b and mold 51 are exaggerated in FIG.15. These tolerances are small enough to achieve the centeringtolerances set out below.

Vertical position of core 14 in ball cup 46' is accomplished usingmachined collars 84, 85 which slip over pins 72', 73' as shown. Setscrews 82 are used to hold collars 84, 85. The length of collars 84, 85determines the distance between cup plate 44b and mold halves 51', 59'and thereafter the position of core 14 (not shown) in cup 46'. Cup 46'is not adjustable in this embodiment but is held in fixed relationshipto plate 44b' with fasteners 83a-c.

As in the other fixture embodiment, core 14 can, using this embodiment,be located up to 0.005 of an inch in any direction from the theoreticalcenter.

Prior to proceeding with cover formation regular mold halves 51b, 51care preheated to 140-180° F., the prepolymer is preheated and degassedat 140-160° F. and the curative is also preheated and degassed at atemperature of 140-160° F. As so preheated, the prepolymer and curativeboth have approximately viscosities of 2000 cps.

The cover material used in the present method is polyurethane which isthe product of a reaction between a polyurethane prepolymer and a curingagent. The polyurethane prepolymer is a product formed by a reactionbetween a polyol and a diisocyanate. The curing agent is either apolyamine or glycol. A catalyst may be employed to promote the reactionbetween the curing agent and the polyurethane prepolymer.

Suitable polyurethane prepolymers for use in the present invention aremade from a polyol, such as polyether, polyester or polylactone, and adiisocyanate. Suitable diisocyanates for use in the present inventioninclude 4,4'-diphenylmethane diisocyanate (MDI) and3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI) and toluenediisocyanate (TDI).

Suitable polyether polyols include polytetramethylene ether glycol;poly(oxypropylene) glycol; and polybutadiene glycol. Suitable polyesterpolyols include polyethylene adipate glycol; polyethylene propyleneadipate glycol; and polybutylene adipate glycol. Suitable polylactonepolyols include diethylene glycol initiated caprolactone; 1,4-butanediolinitiated caprolactone; trimethylol propane initiated caprolactone; andneopentyl glycol initiated caprolactone. The preferred polyols arepolytetramethylene ether glycol; polyethylene adipate glycol;polybutylene adipate glycol; and diethylene glycol initiatedcaprolactone.

Suitable curatives for use in the present invention are selected fromthe slow-reacting polyamine group consisting of3,5-dimethylthio-2,4-toluenediamine;3,5-dimethylthio-2,6-toluenediamine; N,N'-dialkyldiamino diphenylmethane; trimethylene-glycol-di-p-aminobenzoate;polytetramethyleneoxide-di-p-aminobenzoate; or a difunctional glycol;and mixtures thereof. 3,5-dimethylthio-2,4-toluenediamine and3,5-dimethylthio-2,6-toluenediamine are isomers and are sold under thetrade name ETHACURE® 300 by Ethyl Corporation. Trimethyleneglycol-di-p-aminobenzoate is sold under the trade name POLACURE 740M andpolytetramethyleneoxide-di-p-aminobenzoates are sold under the tradename Polamine by Polaroid Corporation. N,N'-dialkyldiamino diphenylmethane is sold under the trade name UNILINK® by UOP.

Suitable difunctional glycols are 1,4-butanediol; 1,3-butanediol;2,3-butanediol; 2,3-dimethyl-2,3-butanediol; dipropylene glycol; andethylene glycol. Difunctional glycols are inherently slow-reacting.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in motorized mixer 60 (FIG. 6) including mixing head 61 byfeeding through lines 63 and 64 metered amounts of curative andprepolymer. The mixer 60 is cooled by cooling jacket 66. Due to theexothermic reaction of prepolymer and curative as mixed, the mixing headtemperature will tend to rise. To control such a rise, the mixing headtemperature is maintained by cooling in a range appropriate for thespecific urethane material and to attain a workable gel time. From thetime mixing commences until the reacting material is fed into each topmold 51a, b, c, etc. or bottom mold half 59a, b, c etc. is about 4-7seconds. Top preheated mold halves 51a, b, c etc. are filled and placedin fixture unit 30 using pins 72, 73 moving into holes 71a, 71b in eachmold 51a, b, c etc. After the reacting materials have resided in topmold halves 51a, b, c, etc. for about 50-80 seconds, a core 14 islowered at a controlled speed into the gelling reacting mixture bylowering frame unit 44 using an pneumatic powered arrangement not shown.Alternatively, electric or hydraulic systems may be used. Controlledlowering is accomplished by adjustment of the powered arrangement and byuse of pneumatic controls not shown to lessen and preferably prevent airbubbles. Stop 39b limits movement downward. The amount of mixtureintroduced into each mold half 51a is 5.4-5.7 g. At a later time abottom mold half 59 of a series of bottom mold halves 59a, 59b, etc. hassimilar mixture amounts introduced into its cavity 58 (FIG. 6).

Upon location of the coated core 14 in halves mold 51a, b, c aftergelling for 50-80 seconds, the vacuum is released in line 46a allowingcore 14 to be released. Mold halves 51a, b, c with core 14 andsolidified cover half 80 thereon is removed from the centering fixtureunit 30, inverted (see FIG. 6) and mated with other mold halves 59a, b,c which, at an appropriate time earlier have had a selected quantity ofreacting polyurethane prepolymer and curing agent introduced therein tocommence gelling.

When a plurality of mold halves 51a, b, c etc. and 59a, b, c etc. arefilled and clamped at one time, the following time sequence ispreferred.

The sequence of introducing the polyurethane mix into the top mold half51a (1T) and its mate the bottom mold half 59a (1B) is as follows:Introduction of the mixed prepolymer and curative into the top mold 51astarts the time sequence which start is referred to herein as time zero.The top half mold 51a receives the mix first at time zero and shortlymold half is placed in fixture unit 30. The core is initially insertedin the mix located in top mold 51a at time 60 seconds (see FIG. 10). Attime 72 seconds, bottom mold half 59a (1B) is filled and at time 132seconds, the mold halves 51a, 59a (1T-1B) are mated and clamped. At time126 seconds, the mix has been in top half 51a 126 seconds and mix hasbeen in bottom half 50a for 60 seconds. The sequence of filling othermold halves 51b (2T) and 59b (2T) and so forth follows a similarpattern. Within this sequence of mixing and dispensing of the prepolymerand curative commences at -4 to -7 seconds.

The thorough mixing that takes place in mixer 60 for the period of timedescribed provides an improved cover material. Mold halves 51, 53 arepre-heated to 160-190° F. The core is held in its fully-down positionfor 30-40 seconds and the vacuum is then released. Following clamping ofmold halves, the clamped mold is put in a curing oven for approximately10 minutes to reach a mold temperature of 140-180° F. followed bycooling for approximately 10 minutes to reach a mold temperature of50-70° F.

The mold halves are clamped together under 400-600 psi pressure. Themold halves each contains sufficient reacting material to formhemispherical portions of the cover. Mold halves are held together for10-15 minutes and thereafter cooled from 140° F.-180° F. to 50° F.-70°F. and then opened to demold the ball. Excess polyurethane is extrudedfrom the mold cavity into sprue channels 51s forming solidified spruesnot shown.

EXAMPLE I

A wound center was dipped in a 30% pre-vulcanized latex solution,drained and partially dried in a current of warm air. Remainder ofdrying was accomplished at room temperature. Latex penetration wasapproximately 50 mils. A mold half was preheated to approximately 160°F.

A mixture of 100 parts of Betathane 23.711, an MDI-based polyetherprepolymer, 5.19 parts of titanium dioxide dispersion and 48.27 parts ofPolamine 250 was prepared. Approximately 5.6 g of this mixture wasdispensed into a heated mold cavity and allowed to thicken forapproximately one minute. A dipped wound core with a diameter of 1.580"was placed in the bottom mold cavity by means of the centering fixtureshown in FIG. 3. The core was held in a concentric position forapproximately 40 seconds to allow the material to thicken further tosupport the core. The top heated mold half was then filled and thematerial allowed to thicken for approximately 1 minute. The top andbottom mold halves were then assembled and clamped by bolts or anyconventional manner. The assembled mold was introduced into a curingoven and cured for 10 minutes at approximately 160° F. The assembledmold was then introduced into a cooling chamber for approximately 10minutes to reach a mold temperature of 50-70° F.

The resulting cover was approximately 50 mils thick on a side and had aShore D durometer of approximately 58-60 when measured after a two-daywaiting period. Subsequently, the ball was painted and the cover wasobserved to be highly abrasion and cut resistant. Spin rate of this ballwas approximately 100-200 rpm lower than a balata covered ball(Tour 100)with an acceptable velocity of 252.7 ft/sec.

EXAMPLE II

The steps of Example I were carried out except that the wound core wasnot dipped in a latex solution.

EXAMPLE III

The steps of Example I were carried out except that a solid core wasused.

EXAMPLE IV

The steps of Example I were carried out with a solid core without alatex dip.

A range of core sizes that can be employed in this invention, whetherdipped or non-dipped, is 1.560" to 1.610" was determined by previoustesting that as core size of the ball increases, ball velocity increases(FIG. 11). However, if the durometer of the cover remains the same, spinrate of the ball was materially unaffected. Spin rate can be changed bymodifying the durometer of the cover by selecting different ratios ofmaterials or combining other materials. Cover durometers of 48 Shore Dto 72 Shore D are attainable with the preferred range of 58-62 for thistype of ball.

The relationship between durometer and spin rate was determined to belinear with harder durometer covers producing lower spin rates (FIG.12).

We claim:
 1. In a method of making a golf ball having a core and outercover and using first and second mold halves, the improvementcomprising:a) placing a first portion of polyurethane in a first cavityof the first mold half; b) allowing said first portion of polyurethaneto partially cure to a selected state of gel in said first cavity: c)positioning said core within said first cavity while vertically andlaterally centering said core within said first cavity to mold saidfirst portion of said polyurethane at said selected state of gel aroundsaid core to the extent the core is positioned within said cavity toprovide a cover half for a first half of said core; d) placing a secondportion of polyurethane in a second cavity of the second mold half at atime subsequent to the placing of said first portion of polyurethane insaid first cavity of said first mold half; e) allowing said secondportion of polyurethane to partially cure to the same selected state ofgel as the first portion was when the core was moved into said firstcavity of said first mold half; f) mating said first mold half, havingthe core and cover half, against said second mold half when said secondportion of said polyurethane in said second cavity of the second moldhalf is at the same selected state of gel as the first portion was whenthe core was moved into said first cavity of said first mold half; saidmating including positioning a second half of said core within saidsecond cavity and molding said second portion of said polyurethane atsaid selected state of gel around said second half of said core; and g)curing the polyurethane in the mated mold halves.
 2. The method of claim1 further comprising the step of encapsulating the core with coatingprior to placing the core in the first cavity.
 3. The method of claim 2wherein the step of encapsulating the core is comprised of dipping thecore in a thermosetting latex bath.
 4. The method of claim 1 furthercomprising inserting an alignment pin into an alignment aperture of thefirst mold half when the core is moved into the first cavity of thefirst mold half so the core is centered in the first mold cavity.
 5. Themethod of claim 1 further comprising limiting movement of the core bystopping vertical movement at a predetermined height with a stop member.6. The method of claim 1 further comprising:a) aligning the first moldhalf with an alignment rail to position the first mold half in a firstdirection; and b) aligning the first mold half with a second member toposition the first mold half in a second direction perpendicular to thefirst direction.
 7. The method of claim 1 further comprising preheatingthe mold halves to 140°-180° F.
 8. The method of claim 1 furthercomprising mixing a prepolymer and a curative to form the polyurethane.9. The method of claim 8 further comprising preheating the prepolymerand curative to 140°-160° F.
 10. The method of claim 8 wherein theprepolymer and curative are mixed for about 4-7 seconds.
 11. The methodof claim 1 wherein the step of allowing the first portion ofpolyurethane to partially cure to a selected state of gel comprisesallowing the polyurethane to reside in the first cavity of the firstmold half for about 50 to 80 seconds.
 12. In a method of making a golfball having a core and outer cover and using first and second moldhalves, the improvement comprising:a) placing a first portion ofpolyurethane in a first cavity of the first mold half; b) curing thefirst portion in the first cavity for a selected amount of time to aselected state of gel; c) positioning said core within said first cavitywhile vertically and laterally centering said core within said firstcavity to mold said first portion of said polyurethane at said selectedstate of gel around said core to the extent the core is positionedwithin said cavity to provide a cover half for a first half of saidcore; d) placing a second portion of polyurethane in a second cavity ofthe second mold half at a time subsequent to the placing of said firstportion of polyurethane in said first cavity of said first mold half; e)curing the second portion in said second cavity for said selected amountof time to said selected state of gel; f) mating said first mold half,having the core and cover half, against said second mold half when saidsecond portion of said polyurethane in said second cavity of the secondmold half is at the same selected state of gel as the first portion waswhen the core was moved into said first cavity of said first mold half;said mating including positioning a second half of said core within saidsecond cavity and molding said second portion of said polyurethane atsaid selected state of gel around said second half of said core; and g)curing the polyurethane in the mated mold halves.
 13. The method ofclaim 12 wherein the step of curing the first portion of polyurethanefor a selected amount of time is about 50 to 80 seconds.